Dual cassette load lock

ABSTRACT

A workpiece loading interface is included within a workpiece processing system which processes workpieces, typically wafers, in a vacuum. The workpiece loading interface includes two separate chambers. Each chamber may be separately pumped down. Thus, while a first cassette of wafers, from a first chamber is being accessed, a second cassette of wafers may be loaded in the second chamber and the second chamber pumped down. Each chamber is designed to minimize intrusion to a clean room. Thus a door to each chamber has a mechanism which, when opening the door, first moves the door slightly away from an opening in the chamber and then the door is moved down parallel to the chamber. After the door is opened, a cassette of wafers is lowered through the opening in a motion much like a drawbridge. The cassette may be pivoted within the chamber when the position from which wafers are accessed from the cassette differs from the position from which the cassette is lowered out of the chamber.

BACKGROUND

[0001] The present invention relates to a front end loading interfaceused in the loading of workpieces in semiconductor processing equipment.

[0002] Semiconductor processing equipment often has a plurality ofchambers in which processing occurs. Arm assemblies or other roboticdevices are generally used to move workpieces, generally wafers from awafer queuing station to various chambers for processing. When theprocessing is finished the wafer is returned to the queuing station. Foran example of prior art processing equipment, see U.S. Pat. No.4,715,921 issued to Maher, et al. for a Quad Processor.

[0003] Semiconductor processing is typically done in a vacuum.Therefore, a wafer queuing station into which is placed a cassette ofwafers to be processed must be pumped down before the wafers may beaccessed. This significantly increases the time the semiconductorprocessing equipment is idle while waiting for a cassette of processedwafers to be exchanged for a cassette of unprocessed wafers andsubsequent pumping down of the wafer queuing station.

SUMMARY OF THE INVENTION

[0004] In accordance with the preferred embodiment of the presentinvention, a workpiece loading interface is presented for inclusionwithin a workpiece processing system. The workpiece loading interfaceincludes two separate chambers. Each chamber may be separately pumpeddown. Thus, while a first cassette of workpieces, typically wafers, froma first chamber are being accessed, a second cassette of wafers may beloaded in the second chamber and the second chamber may then be pumpeddown. This can significantly increase throughput of wafers through theworkpiece processing system.

[0005] In the preferred embodiment, each chamber is designed to minimizeintrusion to a clean room. Thus a door to each chamber has a mechanismwhich, when opening the door, first moves the door slightly away from anopening in the chamber and then the door is moved down parallel to thechamber. After the door is opened, a cassette of wafers is loweredthrough the opening in a motion much like a drawbridge. The cassette ofwafers is on a support with no side panels, facilitating the replacementof a cassette of processed wafers with a cassette of unprocessed wafersby an automated device. The cassette may be pivoted within the chamberwhen the position from which wafers are accessed from the cassettediffers from the position from which the cassette is lowered out of thechamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 shows a top view of a block diagram of semiconductorprocessing equipment which includes two cassette load locks inaccordance with the preferred embodiment of the present invention.

[0007]FIG. 2 shows a block diagram of a load lock which is part of thesemiconductor processing equipment shown in FIG. 1 in accordance withthe preferred embodiment of the present invention.

[0008]FIG. 3 shows a second block diagram of the load lock shown in FIG.2 in accordance with the preferred embodiment of the present invention.

[0009]FIG. 4 shows another block diagram of the load lock shown in FIG.2 in accordance with the preferred embodiment of the present invention.

[0010]FIG. 5 is a block diagram of a cassette wafer holder in a positionextended out of the load lock shown in FIG. 2 in accordance with thepreferred embodiment of the present invention.

[0011]FIG. 6 is a block diagram of the cassette wafer shown in FIG. 5 inan upright position within the load lock shown in FIG. 2 in accordancewith the preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] In FIG. 1, a top view of semiconductor processing equipment 1 isshown. Semiconductor processing equipment 1 may be used, for example,for etching wafers.

[0013] Semiconductor processing equipment 1, includes, for example, aprocessing chamber 3, a processing chamber 4, a processing chamber 5 anda processing chamber 6. A central chamber 2 may be used to temporarilystore wafers on robotic equipment 7 when wafers are being moved to orfrom various of the processing chambers.

[0014] Semiconductor processing equipment 1 also includes dual cassetteload locks. In chamber 8, a wafer cassette 16 holds wafers 10. Inchamber 9, a wafer cassette 17 holds wafers 11. Wafer tray 17 pivotsaround a pivot point 15. When wafers 11 from tray 17 are accessed bysemiconductor processing equipment 1 for processing, wafer tray 17 isflush against a gate 13, as shown, and easily accessed by roboticequipment 7 for transportation into central chamber 2. When wafer tray17 is ready to be removed from chamber 9, wafer tray 17 is pivoted backfrom gate 13 in preparation for the opening of chamber 9 and removal ofwafer tray 17.

[0015] Similarly, wafer tray 16 pivots around a pivot point 14. Whenwafers 10 from tray 16 are accessed by semiconductor processingequipment 1 for processing, wafer tray 16 is flush against a gate 12 andeasily accessed by robotic equipment 7 for transportation into centralchamber 2. When wafer tray 16 is ready to be removed from chamber 8,wafer tray 16 may be pivoted back an angle 18 from gate 12, as shown, inpreparation for the opening of chamber 8 and removal of wafer tray 16.In the preferred embodiment, angle 18 is about twenty-one degrees.

[0016] Chamber 8 and chamber 9 may be separately and individually pumpeddown. A vacuum pump 19 is able to provide a vacuum in chamber 8. Avacuum pump 20 is able to provide a vacuum in chamber 9. In FIG. 1,vacuum pumps 19 and 20 are shown in schematic form. Typically pumps 19and 20 would reside within semiconductor processing equipment 1.Further, while FIG. 1 shows two separate pumps, a single pump could beused to separately and individually pump down chamber 8 and chamber 9.

[0017]FIG. 2 shows a simplified block diagram front view of waferchamber 8. In the preferred embodiment, the volume of chamber 8 is 46liters. A door 21 is shown in a closed position. Door 21 includes anobservation window 22. Door 21 is opened and closed using a pneumaticactuator within a rod 24. Magnets in the pneumatic actuator interfaceattract an outer ring 26. Outer ring 26 is connected to door 21 throughan assembly 23.

[0018]FIG. 3 shows door 21 lowered into an open position. An opening 25,for example, may be fifteen inches high and ten and one half incheswide. By opening down, the intrusion of door 21 into a clean room may beminimized. In the preferred embodiment the total intrusion is about oneinch.

[0019] Once door 21 is lowered, wafer tray 16, on a support structure43, may then be lowered out of chamber 8, much like a draw bridge islowered at a castle entrance. Wafer tray 16 may then be removed and anew wafer tray placed upon support structure 43. Support structure 43 isdesigned with a hollow bottom so that when door 21 is opened and wafertray 16 is lowered, a laminar airflow may sweep downward through wafers10.

[0020] In FIG. 4, additional detail of the mechanism which controls theopening and shutting of door 21 is shown. A side panel 31 of door 21 isconnected to a carriage 30 by a spring 34, a link 36 and a link 35. Ascontrolled by the pneumatic actuator within rod 24, door 21 travels upand down parallel to a rail 50. When being closed, door 21 is stopped byan abutment 32; however, carriage 30 continues upward, expanding spring34, until a gap 33 is completely closed. While carriage 30 continuesmoving upward, a pivot 39 connected to link 36, and a pivot 40 connectedto link 35 continue moving upward. However, a pivot 37 connected to link36 and a pivot 38 connected to link 35 cause door 21 to move towardscarriage 30. Therefore, as gap 33 is closed, links 35 and 36 translatethe upward motion of carriage 30 into horizontal motion of door 21. Door21 is thus brought snug against, and hence seals chamber 8.

[0021] When door 21 is opened, spring 34 compresses causing gap 33 toreappear and links 35 and 36 to straighten, thus moving door 21horizontally away from chamber 8.

[0022]FIGS. 5 and 6 show a block diagram of one possible implementationof an assembly for guiding the lowering and raising of support structure43. In FIG. 5, support structure 43 and cassette 16 are shown loweredout of chamber 8. A roller 44 connected to support structure 43 is shownresting on an extension of a cam containing slot 46 within chamber 8. Aroller 45, also connected to support structure 43, is shown at a firstend of a slot track 46.

[0023] In FIG. 6, support structure 43 and cassette 16 are shown in theupright position within chamber 8. In this position, wafers 10 arehorizontal and are stacked so that they are ready to be accessed bysemiconductor processing equipment 1. When support structure 43 andcassette 16 are in the upright position, roller 45 is rolled to a secondend of slot track 46 and roller 44 rests against a stop 49. Stop 49 isan extension of the cam which contains slot 46.

What is claimed is:
 1. A workpiece loading interface for a workpieceprocessing system including a vacuum chamber, comprising: a workpieceload chamber coupled to the vacuum chamber via a gate, the workpieceload chamber having an opening; and a workpiece support pivotallymounted within the workpiece load chamber, the workpiece supportpivoting between a first pivot position in which the workpiece supportis aligned with the gate and a second pivot position in which theworkpiece is aligned with the opening.
 2. The workpiece loadinginterface according to claim 1 , wherein the workpiece support pivotsabout a substantially vertical axis.
 3. The workpiece loading interfaceaccording to claim 1 , wherein the workpiece support pivots between thesecond pivot position and a third pivot position, the workpiece supportmoving through the opening when pivoting between the second and thirdpivot positions.
 4. The workpiece loading interface according to claim 3, wherein when the workpiece support pivots between the first and secondpivot positions, the workpiece support pivots through a first angle ofapproximately twenty-one degrees, and when the workpiece support pivotsbetween the second and third pivot positions, the workpiece supportpivots through a second angle of approximately ninety degrees.